1. Field of the Invention
The present invention relates to a process for producing a desalted milk by subjecting whole milk, whey, permeate, mother liquor, skim milk, buttermilk, or the like (hereinafter called a "raw milk") successively to electrodialysis, cation exchange process and exchange process, and more specifically to a process for producing a desalted milk, which has desired pH and ash content, in a similar manner without using a neutralizer or the like.
2. Description of the Related Art
Raw milks have heretofore been used widely as they are or after removal or desalting of ash or drying into powder depending on their application purposes, namely, as beverage or as raw materials for foods or other beverage, for example, as raw materials for market milk, confectionery, bread, infant formula and the like.
In many of such applications, desalting is needed since ash tends to affect the flavor and the like. The use of a desalted raw milk is essential for the production of infant formula in particular, because the ash content is specified not to exceed 2.2 wt % by law. Known desalting methods include (1) treatment of a raw milk by electrodialysis, (2) treatment with both a cation exchange resin and an anion exchange resin, (3) treatment by electrodialysis to desalt a portion of salt, followed by treatment with both a cation exchange resin and an anion exchange resin.
Of these three methods, the method (3) is used more often for its superior overall economy, including both initial and running costs, and also its capability of achieving desalting to a higher degree compared with the methods (1) and (2).
Depending on the application purpose, pH adjustment may be needed for a desalted milk after the desalting treatment since the pH has been changed by the desalting treatment no matter which one of the above methods was employed.
Known methods for the above pH adjustment include (1) incorporation of a neutralizing agent such as sodium hydroxide or potassium hydroxide in a desalted milk (U.S. Pat. No. 4,138,501) and (2) addition of an undesalted milk to a desalted milk (French Patent 1,523,106).
These methods (1) and (2) are however accompanied by one or more problems. In the case of the method (1) featuring the addition of a neutralizing agent, sodium or potassium which is a sort of ash is contained at a high level as a result of the neutralization. Turning to the method (2) in which an undesalted milk is added, the addition of the undesalted milk results in an increase of the ash content of the desalted milk by the ash contained in the undesalted milk, whereby the desalting treatment may be rendered meaningless.
In other words, these methods are accompanied by the problem that the desired ash content cannot be achieved if the emphasis is placed on the pH adjustment of the desalted milk whereas the intended pH adjustment cannot be attained if the primary concern is concentrated on the ash content.